In the optical and electronic equipment field, transparent resins are used for optical members such as optical films, optical sheets, transparent substrates, lenses, etc. Resins used for such optical applications are broadly divided into thermoplastic resins and thermosetting resins, and as the thermoplastic resins, an acrylic resin such as polymethyl methacrylate, a polycarbonate, a cycloolefin polymer, a fluorine resin such as CYTOP (registered trademark, manufactured by Asahi Glass Company, Limited), etc. are known. As the thermosetting resins, an epoxy resin, a silicone resin, etc. are known.
In recent years, in the optical and electronic equipment field, use of high intensity laser light or blue light, or near-ultraviolet light, is spread, and a resin excellent in transparency, heat resistance and light resistance has been demanded.
In general, a thermoplastic resin is softened and flows at a high temperature, and therefore, it is not suitable for use at a significantly high temperature. On the other hand, a thermosetting resin has at least two crosslinkable functional groups, and when heated or irradiated with light, it will be cured by a reaction of the crosslinkable functional groups one another. Its cured product is less likely to flow even at a high temperature and has high heat resistance, and thus, it is suitable for use at a high temperature.
Among such thermosetting resins, an epoxy resin is excellent in heat resistance. However, a usual epoxy resin has an aromatic ring and is not sufficiently transparent in a near ultraviolet region from ultraviolet. An alicyclic epoxy resin having no aromatic ring can form a cured product excellent in transparency even in a near ultraviolet region from ultraviolet (Patent Document 1). However, the cured product is not sufficient in heat resistance and light resistance. A silicone resin can form a cured product which is excellent in transparency from a visible light range to a near ultraviolet region and excellent in light resistance and heat resistance (Patent Document 2). However, the cured product has a large thermal expansion coefficient and a large permeability of gas such as moisture and oxygen, which may cause problems in the reliability of the electronic device.
In recent years, in order to meet the demand for larger capacity and higher speed of information processing in optical communication systems and computers, optical transmission systems have come to be used. There is an optical waveguide as a basic constituting component in an optical device or the like to be used in an optical transmission system. As a resin-type optical waveguide, an optical waveguide having a fluorinated polyimide as the constituting component (Patent Document 3) is, for example, known.
However, a fluorinated polyimide is brittle, and its elastic modulus is high, so that it may undergo warpage in the production process. Further, for such a fluorinated polyimide, a special monomer is required, which is expensive and lacks in applicability to the production of general-purpose optical waveguides.
Thus, a novel compound is desired which is a curable compound having at least two crosslinkable functional groups and which is capable of producing a cured product that sufficiently satisfies characteristics required for optical members such as optical characteristics such as transparency, heat resistance, mechanical properties, etc.